Electricity is the flow of electrical charge from a higher potential to a lower potential. The energy that results from the flow of electrical charge has been employed in myriad applications, including transportation, heating, lighting, and communications, among others. Because of electricity's extensive utility in the modern world, numerous devices and systems require access to this flow of electrical charges in order to function. Whether it's heating a filament in a light bulb, powering a motor in an electric car, or flowing through complex circuits inside a computer, electricity must be controlled and manipulated to meet the various energy requirements of countless devices.
The “amount of electricity” in a flow of charges is characterized by current and voltage. Generally, current is the volume or quantity of charge flowing in a circuit and voltage is the energy carried per unit charge. If too much electricity, either current or voltage, flows through a given circuit, the components of that circuit may be damaged or destroyed. Conversely, if not enough electricity is supplied to a system, it may not function properly, if it is able to function at all. In other words, it is very difficult for electrical control systems to effectively manipulate the flow of electrical charges so that the supply meets the demand in both quantity and quality.
For example, conventional control systems in automobile engines are designed to manage varying power demands by increasing power output when a driver presses down on the gas pedal (e.g. in order to accelerate the vehicle or to maintain a constant speed while climbing a hill). In another example, a coal power plant is designed to meet the demands of an electrical grid by controlling the quantity of coal entering the boiler, which in turn affects the rate of steam formation and thus affects the power produced in the turbine generators. In other electrical systems, such as in residential wiring or in complex computer circuits, safety mechanisms are used to ensure that excess current and voltage do not damage or destroy components of the system. For example, without fuses and circuit breakers, many household items would be damaged if an event caused a dramatic rise in the voltage flowing through residential wiring. In computer circuits, amplifiers and resistors can be used to increase or decrease the voltage and current that flow to individual components in the circuit.
The problem with these conventional power schemes and electrical systems is their inefficiency in managing varying supplies and/or varying demands. Continuing with the examples above, increasing and decreasing an automobile engine's RPM to meet acceleration demands can cause the engine to operate at other than optimal efficiency. Also, controlling power generation by altering the input flow of coal involves a substantial delay in response time, which can result in either a temporary excess or a shortage of power. Conventional power plant control systems may attempt to mitigate this problem by storing excess energy via pumped hydro-electric storage or by quickly generating more energy by introducing natural gas into the boiler; however, these measures decrease the total efficiency of power generation. In conventional household wiring and computer circuits, electrical control systems attempt to manage varying energy supplies by providing energy sinks or circuit breaks to protect sensitive components.
Thus, regardless of whether a control scheme is employed on the supply side (controlling energy source input flow) to meet a varying demand or on the demand side (providing sacrificial energy sinks or circuit breaks) to meet a varying supply, conventional electrical systems are often inadequate in efficiently managing a the varying supply and demand requirements of loads that draw upon them.